Currently available dispensing devices for dispensing fluid material, and in particular multiple component adhesive materials, in predetermined desired ratios often use a conventional cartridge type dispenser which includes a piston engaged within the cartridge to dispense the desired amount of fluid. Such devices are often used in connection with the mixing of multiple component reactive materials containing volatile organic compounds or VOC's. Unfortunately, such devices have a tendency to leak, and do not provide consistent repeatable shot sizes of each of the material components.
Further, such prior art devices typically do not pump the different adhesive material components in various ratios or desired amounts. As a result, premixing of the separate components in the desired formula is required prior to pumping. Such premixing exposes the pump operator to component materials which may give off undesirable fumes, and which are difficult to clean up in the event a spill occurs during the premixing operation. Additionally, the premixing of such materials also results in an increased amount of waste product due to the reduced life of the materials once exposed, for example in open containers, for mixing.
Available prior art devices also do not allow the material components being pumped to be changed to different materials, without further cleaning of the devices. Moreover, the devices typically force the component materials from their respective cartridges under pressure. Such pressurized application can additionally result in leakage and inconsistent shot sizes of the desired component materials being applied. Although attempts have been made to deliver such material components individually using a fixed gear ratio assembly, such fixed gear ratio devices do not maintain the desired ratios of component materials for materials having different viscosities.